In manufacturing a semiconductor device, a process for forming a wiring such as an interconnection line or contact is carried out. Conventionally, as such a process, a damascene process has been used. In the damascene process, a groove or a hole is formed at an interlayer insulating film by etching, and a metal material is buried in the formed groove or hole. However, along with a recent trend of miniaturization of wiring, the damascene process is accompanied by various problems such as difficulty in burying a metal material in a fine hole or groove.
In order to solve the above-described problem of the damascene process, there has been suggested a process in which a copper layer is formed first and a fine copper wiring is formed by etching the copper layer. Such a process is described in Non-Patent Document 1. In the process described in Non-Patent Document 1, a copper layer is etched by exposing the copper layer to plasma of a processing gas containing a hydrogen gas and an argon gas.    Non-Patent Document 1: Fangyu Wu et al., “Low-Temperature Etching of Cu by Hydrogen-Based Plasmas”, ACS APPLIED MATERIALS & INTERFACES, 2010, Vol. 2, No. 8, p. 2175-2179